Abstract
ABSTRACT Large-scale observations of the Perseus Molecular Cloud (MC) with Nanshan 26-m telescope are presented using the 6 cm ortho-H2CO (110–111) transition. As a probe of dense gas at low temperatures, the H2CO absorption extends over the main parts of the Perseus MC. A comparison of the H2CO absorption line with the 12CO and 13CO (J = 1–0) emissions shows that the H2CO and CO are similarly distributed over the Perseus but that H2CO correlates better with 13CO. Comparison with the Herschel-derived H2 column density shows that both the 13CO and H2CO column densities vary linearly with the H2 column density. The main parameters of H2CO absorption line data show a log-normal distribution, which suggests that the strong non-thermal line-broadening results from large-scale supersonic turbulence related to the star formation. Formaldehyde absorption serves well as a tracer of star formation activity and also the H2CO-to-13CO and H2CO-to-H2 abundances systematically trace the star formation activity in the six subregions of Perseus MC. The H2CO abundances anticorrelate with the number of prestellar and protostellar cores and the IRIS 12 μm flux in the six subregions and reveal the star formation history in the Perseus MC.